CentOS - Jul 2011 - how to enable Flow Control on CentOS?

Hi,

I have an interesting situation with one of our switches. It's a
D-Link DGS-3100, 24 port 10/100/1000 Layer 2 Managed switch with some
CentOS servers connected to it. On many of the servers I need to
disable Flow Control on the switch's ports otherwise the CentOS
server's doesn't connect to the switch. i.e. the Switch indicates that
the LAN cable is unplugged and CentOS can simply not connect to any
host on the LAN.

As soon as I disable Flow Control, CentOS "breaks".

Does anyone know why this would happen, or how / if I can enable Flow
Control in CentOS as well?



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Kind Regards
Rudi Ahlers
SoftDux

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On 07/07/2011 07:46 AM, Rudi Ahlers wrote:
> Hi,
>
> I have an interesting situation with one of our switches. It's a
> D-Link DGS-3100, 24 port 10/100/1000 Layer 2 Managed switch with some
> CentOS servers connected to it. On many of the servers I need to
> disable Flow Control on the switch's ports otherwise the CentOS
> server's doesn't connect to the switch. i.e. the Switch indicates
that
> the LAN cable is unplugged and CentOS can simply not connect to any
> host on the LAN.
>
> As soon as I disable Flow Control, CentOS "breaks".
>
> Does anyone know why this would happen, or how / if I can enable Flow
> Control in CentOS as well?
I've got many CentOS machines connected to a few DGS-3100 (24 and 48 
port versions) and I've not seen this problem before. I can't suggest 
what might be the problem, but I am going to guess that it's server side.

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On Friday, July 08, 2011 07:06:06 PM Les Mikesell wrote:
>And the 
> gigabit spec requires auto-negotiation.
According to clause 37.1.4.4 "User Configuration with
Auto-Negotiation" of IEEE 802.3-2008, auto-negotiation with 1000Base-X is
optional, but encouraged.

In contrast, for 1000Base-T, we find the following information in clause 40.5.1:
"40.5.1 Support for Auto-Negotiation
All 1000BASE-T PHYs shall provide support for Auto-Negotiation (Clause 28) and
shall be capable of operating as MASTER or SLAVE."

'Shall' being legal language for 'absolutely without a doubt
must' in this case.  Overwise the PHY wouldn't be able to determine
which PHY is the clock MASTER.